2. EOCENE

Titanoboa (40-foot-long snek)

Dawn redwoods (once-widespread conifers, now native to China)

Dawn horses (tiny adorable proto-horses)

Ambulocetus ("walking whales," basically hoofed amphibious carnivores)

Eophyllium (the earliest known leaf-mimicking insects!)

3. JURASSIC

Archaeopteryx (transition between non-avian feathered dinos and modern birbs)

Pleisiosaurs (marine reptiles, e.g., Loch Ness monster)

Turtles (hopefully you& #39;re familiar)

Allosaurus (big bipedal predator dino)

Ginkgo (same as today, plants beat dinosaurs, sorry)

4. PLEISTOCENE

Woolly mammoths (matriarchal icons of the ice age)

Megalodon (definitely extinct)

Giant beaver (did they build dams? Who knows?)

Terror birds (bigger than you, scary, delicious?)

Short-faced bear (bigger than polar bears, scary, YOU& #39;RE delicious)

5. DEVONIAN

Dunkleosteus (huge bitey fish)

Ammonites (squid with spiral shell)

Trilobites (successful for 300 million years!)

Tiktaalik (transition between fish and 4-legged vertebrates; could prop itself up in shallows)

Archaeopteris (tree-like plant with fern-like leaves)